1. Field of the Invention
The present invention relates to supply to carders, in which a thin layer of fibrous material is worked by a series of surfaces, which are provided with a large number of tips with a variety of shapes, inclinations and levels of stiffness, and are driven with motion relative to one another, by means of which the fibrous material is opened up into the form of individual fibres, the particles of dirt are eliminated, the fibres are mingled with one another, and a non-twisted strip of fibres is formed, to be sent to the successive processing stages.
2. Discussion of the Background
In its most general aspects, the operation of supply to a carder of the cotton-industry type is carried out according to the most significant aspects of the diagram illustrated in FIG. 1. The light-coloured arrows indicate the flow of flock fibres, whereas the dark arrows indicate the flow of the conveying and control air.
In general, the untreated material 1, which consists of flock fibres, is obtained from an opener, which is not shown in the figure. It is conveyed by means of pneumatic transport in a current of air, and is accumulated in the end part 2 of the descending duct 3 for intake of the fibres. The transport air is discharged via the apertures 4; as the fibrous material is deposited in the end part 2, it covers these apertures, and increases the pressure in the duct 3. Monitoring of the pressure value in the upper duct makes it possible to measure the level of filling of the chamber or end part 2. On the basis of the level of filling of the latter, there is regulation of the processing, and of the flock fibres conveyed from the preceding series of openers. If the carding unit consists of a plurality of carders in parallel, the flow of fibres which is conveyed from the opener unit upstream, to the carders downstream, is distributed preferentially to the carders, the ducts 3 of which are least filled, and which thus provide a smaller loss of load relative to the flow of fibres.
Downstream from the end part 2, there is disposed the supply cylinder 5, which supplies the flock fibres to the disintegrator cylinder 6, which breaks up the material. The two cylinders operate with rotation which is consistent with one another, in order to transfer the material to the duct 7 below.
The current of air in order to maintain the pressure in the lower chamber 8 at the end of the duct 7, is supplied by means of a blower 10, which supplies a flow of air tangentially relative to the disintegrator cylinder 6, which air is then discharged via the apertures 11. In the duct 7, there is installed a pressure switch, which controls the speed of rotation of the roller 5, such as to regulate the density of the fibres contained in the chamber 8, which form the mat supplied to the carder.
The base of the second descending duct 7 is equivalent to conventional storage of fibres in silos, in which the density of the fibres is controlled and regulated by pneumatic effect.
The set of discharge cylinders or lobar rollers 13, which rotate at a controlled speed, in order to regulate the output of fibres, discharges the fibres onto a slide 14, which supplies the fibres in the form of a mat 15 to the carder. The machine is provided with a supply roller 16, which controls the mat, and presses it against the supply table 17, and supplies a brush of mat to the actual carder. The first carding step is carried out by the opener cylinder 18, which is generally known as the taker-in.
The transverse dimension of the mat supplied is compatible wit h that of the carder processing cylinders; for carders of the cotton-industry type, this transverse dimension is in general between 0.7 and 1.5 metres, depending on the models, and it is essential that this mat is of a regular thickness and density along its entire length, such that the strip which is produced by the carder is processed in a homogeneous manner in the transverse direction.
The present invention relates more specifically to a system for supply to the opening cylinders or taker-in of a carder, in order to obtain a supply of flock fibres which is regular over a period of time, and is distributed homogeneously along the entire length of the carder, both over a period of time and in the cross-section of the conveying ducts, even when the density of the fibres varies.
According to the present state of the art, the technical problem of regularity over a period of time, of the quantity of fibres supplied to the carder, has been dealt with, for example, in U.S. Pat. No. 4,275,483 in the name of Robeson, by arranging the horizontal support shaft of the roller 16 on an oscillating system, which is opposite the fixed tables 17, and forms a guide for conveying the mat towards the taker-in. Depending on the raising thrust exerted by the mat on the roller 16, which is detected by a corresponding sensor to detect the displacements of the roller, the speed of the supply roller 16, i.e. the linear output of the mat, is then varied. This system is sensitive to the average density of the fibrous mass which passes moment by moment beneath the roller 16, but it does not detect in any way whether the fibrous material is well-distributed, and has a homogeneous density in a transverse direction along the entire width of the slide 14, or whether, in contrast, it is concentrated preferentially on one side of the slide or the other. In fact, it is not possible to prevent preferential paths in the descending ducts, although control of the density by means of the current of air in the two ducts 3 and 7 is designed to make the flow and the density of the fibrous flock material more regular.
The volume of fibres thus supplied to the carder, with its transverse irregularities, is worked with the same intensity of opening and cleaning, along the entire width of the cylinders, and for smaller thicknesses or lower densities this can be excessive, and for greater thicknesses or higher densities it can be insufficient. The carder is intrinsically unable to carry out mingling or homogenisation in a transverse direction of the fibres which are presented to the taker-in. If an irregularity of volume or density occurs at the start of the taker-in, at a specific transverse co-ordinate, in general this re-occurs at the same co-ordinate in the final doffer of the carder, thus giving rise to a strip which has an irregular transverse cross-section, depending on the excesses or lacks of material present in the transverse cross-section of the mat.
In addition to this disadvantage, there is irregular wear of all the fixed and mobile lined surfaces, as well as dirtying and irregular clogging of the linings.